Yuki is a “humanoid interface”, or artificial human, created by a god-like alien figure known as the Data Overmind. According to her, the Data Overmind has existed since the Big Bang, and it has been frustrated over the slow pace of evolution. However, three years ago, it had noticed an explosion of data, which was later traced none other than Suzumiya Haruhi. It then created humanoid interfaces like Yuki, strategically placed near Haruhi in hopes of gaining insights by observing the phenomenon.
Cute cosplayer from Japan Comiket 82! She really looks a lot like Yuki especially with this pose. Thanks again to Michelle for sending this in!